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<H3>write_restart command 
</H3>
<P><B>Syntax:</B>
</P>
<PRE>write_restart file 
</PRE>
<UL><LI>file = name of file to write restart information to 
</UL>
<P><B>Examples:</B>
</P>
<PRE>write_restart restart.equil
write_restart poly.%.* 
</PRE>
<P><B>Description:</B>
</P>
<P>Write a binary restart file of the current state of the simulation.
</P>
<P>During a long simulation, the <A HREF = "restart.html">restart</A> command is
typically used to dump restart files periodically.  The write_restart
command is useful after a minimization or whenever you wish to write
out a single current restart file.
</P>
<P>Similar to <A HREF = "dump.html">dump</A> files, the restart filename can contain
two wild-card characters.  If a "*" appears in the filename, it is
replaced with the current timestep value.  If a "%" character appears
in the filename, then one file is written by each processor and the
"%" character is replaced with the processor ID from 0 to P-1.  An
additional file with the "%" replaced by "base" is also written, which
contains global information.  For example, the files written for
filename restart.% would be restart.base, restart.0, restart.1, ...
restart.P-1.  This creates smaller files and can be a fast mode of
output and subsequent input on parallel machines that support parallel
I/O.
</P>
<P>Restart files can be read by a <A HREF = "read_restart.html">read_restart</A>
command to restart a simulation from a particular state.  Because the
file is binary (to enable exact restarts), it may not be readable on
another machine.  In this case, the restart2data program in the tools
directory can be used to convert a restart file to an ASCII data file.
Both the read_restart command and restart2data tool can read in a
restart file that was written with the "%" character so that multiple
files were created.
</P>
<P>IMPORTANT NOTE: Although the purpose of restart files is to enable
restarting a simulation from where it left off, not all information
about a simulation is stored in the file.  For example, the list of
fixes that were specified during the initial run is not stored, which
means the new input script must specify any fixes you want to use.
Even when restart information is stored in the file, as it is for some
fixes, commands may need to be re-specified in the new input script,
in order to re-use that information.  See the
<A HREF = "read_restart.html">read_restart</A> command for information about what is
stored in a restart file.
</P>
<P><B>Restrictions:</B>
</P>
<P>This command requires inter-processor communication to migrate atoms
before the restart file is written.  This means that your system must
be ready to perform a simulation before using this command (force
fields setup, atom masses initialized, etc).
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "restart.html">restart</A>, <A HREF = "read_restart.html">read_restart</A>,
<A HREF = "write_data.html">write_data</A>
</P>
<P><B>Default:</B> none
</P>
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